Display systems have become more complex in recent years. Television receivers, for example, have a greatly increased number of functions available to the user. These functions may include the routing and processing of stereo sound signals, the selection of various auxiliary video sources, the scheduling of future programs, etc. Typically, in order to utilize these functions, a relatively large number of function selection switches are required. This makes the input device such as the hand-held remote control transmitter large, difficult and confusing to use, and expensive to manufacture.
One way to minimize the number of switches on the remote control unit is to provide a display of a matrix of functions displayed on the screen of the display system, in what is sometimes called a menu, and to provide input selection apparatus for selecting which ones of the displayed functions are to be exercised. Menu based systems for use in television receivers are disclosed in U.S. Pat. No. 4,641,205 (Beyers) issued Feb. 3, 1987 and U.S. Pat. No. 4,626,892 (Nortrup et al.) issued Dec. 2, 1986, both of which are assigned to the same assignee as the present application.
The input device for a menu-based system may be a so-called "mouse", a joy stick or a light pen, each of which provides X-axis and Y-axis position information to a display controller for determining the desired function. Typically, the user must use both hands or must have a flat surface on which to move the device. Most of these devices are wired to the controller and therefore do not lend themselves to remote control at distances usually associated with television viewing.
It is desirable, however, that an input device make use of the human propensity to point at a desired item, thus providing ease of operation. Light pens and touchscreens provide such a pointing function but necessarily require the user to be within an arm's length of the display screen. A wireless input device used for pointing to a particular item to be selected from a menu displayed on a display screen is disclosed in U.S. Pat. No. 4,565,999 (King et al.) issued on Jan. 21, 1986.